<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <h1>jsonp</h1>
  <button id="btn">发送jsonp请求</button>
  <script>
    // function callback(data){
    //   console.log("调用了callback",data);
    // }

    // let oscript = null

    // const oBtn = document.getElementById('btn')
    // btn.onclick = function(){
    //   if(oscript){
    //     oscript.remove()
    //   }
    //   oscript = document.createElement('script')
    //   oscript.src = "http://127.0.0.1:3000/userJsonp?cb=callback&userId=001";
    //   document.body.appendChild(oscript)
    // }

    function callback(data){
        console.log("回调被执行了",data);
    }

    let oscript = null

    const oBtn = document.getElementById('btn')
    btn.onclick = function(){
      if(oscript){
        oscript.remove()//删除元素
      }
      oscript = document.createElement('script')
      oscript.src = "http://127.0.0.1:3000/userJsonp?userId=001&cb=callback"
      document.body.appendChild(oscript)
    }


  </script>
</body>

</html>